The experts aren't necessarily credentialed experts as we would typically think of them. You can participate in forecasting tournaments like Good Judgement Proj

The experts aren't necessarily credentialed experts as we would typically think of them. You can participate in forecasting tournaments like Good Judgement Project and if you score high enough you can participate in invite-only events that are in partnership with entities like DARPA. But the people come from all backgrounds- I got all this from the book Superforecasting by Philip Tetlock. Edit: got the title wrong